Scharenberg, R.P.Srivastava, B.K.Pajares Vales, Carlos2020-04-162020-04-162019Scharenberg, R., Srivastava, B. and Pajares, C., 2019. Exploring the initial stage of high multiplicity proton-proton collisions by determining the initial temperature of the quark-gluon plasma. Physical Review D, 100(11), 1140402470-0010http://hdl.handle.net/10347/21462We have analyzed identified particle transverse momentum spectra in high multiplicity events in p p collisions at LHC energies √ s = 0.9 – 13     TeV published by the CMS Collaboration using the color string percolation model (CSPM). In CSPM color strings are formed after the collision, which decay into new strings through color neutral q − ¯ q pairs production. With the increase in the p p collisions energy number of strings grow and randomly statistically overlap producing higher string tension of the composite strings. The net color in the overlap string area is a vector sum of the randomly oriented strings. The Schwinger color string breaking mechanism produces these color neutral q − ¯ q pairs at time ∼ 1     fm /c, which subsequently hadronize. The initial temperature is extracted both in low and high multiplicity events.The shear viscosity to entropy density ratios η / s are obtained as a function of temperature. For the higher multiplicity events at √ s = 7 and 13 TeV the initial temperature is above the universal hadronization temperature and is consistent with the creation of deconfined matter. The η / s is similar to that in Au + Au collisions at √ s N N = 200     GeV . The small value of η / s above the universal hadronization temperature suggested that the matter is a strongly coupled quark gluon plasma. In these small systems it can be argued that the thermalization is a consequence of the quantum tunneling through the event horizon introduced by the quarks confined in the colliding nucleons and their deceleration due to string formation, in analogy to the Hawking-Unruh radiation which provides a stochastic approach to equilibrium. The disk areas cluster on the nucleon transverse collision area. At the 2 D percolation threshold a macroscopic spanning cluster suddenly occurs at the temperature T i = T h , representing a small connected droplet of q − ¯ q pairs, the quark-gluon plasma (QGP). T h is the universal hadronization temperature ∼ 167.7     MeV . The collision energy dependent buildup of the 2D percolation clusters defines the temperature range 159 ± 9     MeV of the crossover transition between hadrons to the QGP in reasonable agreement with the lattice quantum chromodynamics (LQCD) pseudocritical temperature value of 155 ± 9     MeV . Color string percolation model is the new initial stage paradigm for the study of the high density matter produced in p p and A + A collisions. With CSPM we can directly explore the thermodynamics of the QGP above the universal hadronization temperature.engPublished by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOIhttps://creativecommons.org/licenses/by/4.0/journal article10.1103/PhysRevD.100.1140402470-0029open access